Mitochondrial Membrane Damage Is Prevented by an Anthocyanin-Rich Fraction of Callistemon citrinus in 6-OHDA-Exposed SH-SY5Y Cells

Neurodegenerative diseases represent a significant clinical challenge. Understanding the pathogenic mechanisms is essential for developing more effective therapies, and mitochondria appear to play a key role in these processes. Since current treatments are limited to symptom management, natural strategies capable of preserving mitochondrial function could represent a promising preventive and therapeutic approach in neurodegeneration. This study aims at investigating the molecular mechanisms underlying the neuroprotective potential of an anthocyanin-rich extract from Callistemon citrinus flower (Cce) in differentiated SH-SY5Y cells exposed to 6-hydroxydopamine (6-OHDA). Exposure of cells to 6-OHDA inhibited cell viability and caused cell death, events hindered by the pre-treatment with Cce. Furthermore, it restored normal cell cycle distribution, as well as hampered 6-OHDA-induced apoptosis. Given the pro-oxidant effect of 6-OHDA, we observed that Cce reduced reactive oxygen species in stressed SH-SY5Y cells, along with recovering their antioxidant protection system. Focusing on mitochondria, Cce was able to protect their membranes from 6-OHDA, as suggested by the restoration of mitochondrial membrane potential. This led to a reduction in release of cytochrome c and the consequent activation of caspases 9 and 3, characteristic of the intrinsic apoptotic pathway, supporting our initial findings. Our results indicate that Cce prevents SH-SY5Y cell death induced by 6-OHDA via the preservation of mitochondrial integrity mainly through to its antioxidant properties, encouraging further studies to support its exploitation in the management of neurodegeneration.